Aquion Energy batteries

Ah-ha. Thanks for the graph. You are correct - I was thinking backwards.

Update:

• Both stacks functioning properly. No noticeable degradation in the performance.
• I've been keeping them above 15% charge. There were some <5% DOD events, no noticeable effects.
• Don't know exactly how many effective cycles have incurred - I don't have the data and I'm conservative about cycling. They are cycled by roughly 60% per day for 3/4 of the year.
• At 50% I can push about 5A into each stack, in correlation with the documentation. Beyond 80% the charge rate falls into the trickle range (0.5-1A).
• Spring of 2016, pushed the C40's float voltage to 57V. No adverse effects so far.
• Below 40F their charge resistance spikes. Below about 28F they don't present any usable charge or accept charge.
• Had them drop to around -3F, no damage (so far). Wouldn't recommend it.
• They have a high specific heat: I'm seeing about 2 days to adjust to a 20 degree change in air temperature, within 2 degrees. Reminder: They are encased in 3" foam insulation.
• I have temp/voltage CC current logs stored since fall 2015 but warn that the data is dirty due to sensor/communication errors. (I homebrewed with an rPI instead of using the expensive Aquion/Xantrex hardware). If there is interest I suppose I could try cleaning the data and presenting a few graphs.
• Overall they are working as I had expected.
• We've had 3 outages (2hrs, 4hrs, 12hrs ), not including <1hr hiccups and the batteries/solar combo did their job. There is severe flicker when the fridge starts when on batteries alone.

Saw the news about Aquion bankuptcy. My main concern is the status of my warranty. Fortunately I only have a toe in the water with 2 stacks. I don't regret this (yet) - things are still working out.

Have been watching the prices of the Aquion/Aspen over the years and was hoping they would fall by at least 30% but they did not. Then as the Powerwall II started hitting the market the Aquion/Aspen didn't appear that it could compete. Was happy to see that they were splitting them down into 24V stacks as they were not fun to move and install.

Looking forward to seeing this technology again some way or another but the price really needs to fall. Perhaps the aftermarket has some promise, pending cost-effective shipping.

Thanks for the update.

Sounds like those batteries are at least doing what they claim they should. The real test is the total cycles and life span. I hope it works out for your considering your investment.

These are significant issues which make the batteries useless for most applications. That is why they went bankrupt. It all revolves around very high Internal Resistance and extremely steep charge and discharge curves. About their only usable application is egress lighting for long periods.

The very high resistance means they cannot be charged or discharged fast. That is why your lights flicker when the ridge starts, that cannot even handle a small load. In any Solar or Energy Storage you need to be able to charge/discharge at least at C/8 to C/6 in most locations, and some locations as high as C/2. As you mentioned C/40 is about all they can handle. That makes it extremely expensive to have any usable application.

Example in a standard design you size the batteries for 5 day reserve capacity with 3 being usable. Using FLA batteries providing in winter you have at least 2.4 Sun Hours your charge rate will be at the maximum C/8 charge rate, Say you use 1 Kwh/day and with minimum 2.4 Sun Hours in winter requires a 630 watt panel, 52 Amp Charge Current, and a 12 volt 420 AH FLA battery. That will generate the max C/8 charge current for FLA batteries. If you were to do this with Aquion Batteries would require a 2000 AH battery with 20 day reserve capacity to handle a 50 amp charge current. Actually more than that because the charge efficiency is much lower than FLA.

No dang wonder they failed. I knew it immediately because I knew what the numbers meant. Aquion batteries cast 3 times more than FLA and require 5 times more capacity. That makes them 15 times more expensive, To make matters worse the steep discharge curve means 40% of the capacity is not usable. No 12 volt Inverter works down to 8 volts and up to 16 volts. Unfortunately most consumers did not know this and learned the hard way. Between warranty claims and the news finally getting out doomed the company. The technology just will not work.

That is why I scream Bloody Murder when folks come here touting them. Stay far away from them like NiFe batteries. Let some other sucker learn the hard way if they do not want to listen and learn.

Another update:

In spring 2018 (3 years in) I noticed difficulty starting the fridge off of the pair of stacks. Looks like the power handling has degraded. Looking further into capacity, performed a charge/discharge test and got about 1.2kwh/stack when discharging at 75W/stack until 44V cutoff, then switching to 20W/stack and draining them further. Depending on the source (Aquion had a few capacity charts which contradicted each other) the S20 is somewhere between 2.3 and 2.6kWh per stack if currents are kept below 2A/ea. (about 90W/ea.). So this appears to be worse than the expected 30% degradation found in the documentation. As a workaround I wired up a small super-capacitor array and that did the trick to supply the startup draw.

Suspecting a bad cell, I let them settle disconnected after a full charge and checked their individual voltages. There was no change in their voltage from when they were new.

Perhaps this is the real sodium-ion behavior coming through as the additives which enhanced the capacity and power handling are wearing off? It is difficult finding documentation on sodium ion chemistry, for example some other chemistries have known tricks, such as running a few deep-cycles to bring a battery's capacity back, while other battery chemistries are destroyed that way. Aquion did mention in one piece of documentation that a deep cycle might improve them but it's unclear if that applies to older batteries or only for their break-in period.

These batteries are in an environment with a lot of thermal swings, and they could have gotten too cold a few times.

Anyway, I am now reaching the point where they start deviating from what was on paper: 50% degradation at 3 years given 50% DoD cycling. Subjectively, they don't seem to be degrading much after that. I could do another capacity test later in the year and we'll see what's happened.

Have you done another capacity test lately? I am new to these batteries and recently introduced by One of my clients who has three stacks of these. I'll be upgrading them to lithium soon but it's been interesting seeing how these batteries work. Obviously 3 stacks isn't enough to live any sort of normal life off grid. Basically they've been suffering for 7 years because of this chemistry in combination with it being severely undersized for even the most basic need like a few lights & the refrigerator.